In UIM environments with a multi-tier tunnel setup -- meaning a series of hubs with tunnels from A->B->C -- tunnels may appear to be unstable as hubs will lose communication frequently, while configuring probes across the tunnels results in frequent communication errors.  Configuration of the product is difficult due to the instability of the hub-to-hub tunnels.

Release: UIM 20.x
Component:HUB

In order to provide the greatest stability, the following steps should be performed:

    1- upgrade all hubs in the environment to at least 9.33.

    2- upgrade the robot (controller) on all the hubs to at least 9.33.

             (note: as a best practice, it would be advisable to upgrade all robots in the entire environment to 9.33, not just the hub robots.)

    3- add the following configuration key/value to the <controller> section of the robot.cfg:

        reuse_async_session = 1

    4- add the following configuration keys/values to the hub.cfg:

        in the <hub> section:

        check_spooler_sessions = 1

        in the <tunnel> section:

        protocol_mode = 3

        max_heartbeat = 30

   5- Restart the server where the hub probe is installed.

These settings can be applied in any environment but will mostly be applicable to multi-tier tunnel environments.

With protocol_mode=3 you may see what is known as the "Christmas Tree Effect" in Infrastructure Manager - where the icons for hubs are cycling between red/yellow/green frequently; however, if you click on a hub after it has gone red/yellow, it should be immediately available for configuration.

Note that reuse_async_session=1 will be the default setting for robot 7.95 and above, so it would not be a bad idea to put this setting on all robots.  This setting is available starting in robot 7.80HF21.